FIG. 1 shows an outline of a plasma treatment device 100 used in semiconductor manufacturing process. The drawing shows the state where a substrate 130 masked by resist 132 is processed by using plasma 110 in the plasma treatment device 100. Regarding the plasma 110, gas (such as Cl2) is introduced in vacuum (1 Torr to 10−4 Torr), and high-frequency electric field (400 kHz to 2.45 MHz) is applied to generate the plasma 110. By using the plasma 110 and applying substrate power source (400 kHz to 13.56 GHz) to the substrate 130 masked by the resist 132, the processing is performed. In the plasma treatment device, vapor phase reaction control of plasma (distribution control of electron energy, optimizing gas molecule structure, dwell time control, and the like) and surface reaction control of the substrate (substrate temperature control, surface impurity control, reactive product control, substrate bias control, and the like) need to be performed.
As an evaluation method of the plasma treatment device, there is a typical evaluation method using a probe such as Langmuir probe. By the evaluation method using the probe, only the characteristic in the plasma is measured, and the density and the energy of various kinds of particles that are made incident to a material to be processed by the plasma cannot be measured.
In pattern dimensions of a substrate of a material to be processed, which is processed or deposited by the plasma treatment device, microfabrication has been progressed to the order of a few hundred nm. Therefore, needs has been increased for measuring the characteristics of various kinds of particles made incident inside such fine patterns from the plasma.
To measure the characteristics of the particles made incident to the substrate to be processed, pinholes are formed on a flat plate, an energy analyzer of a blocking electric field type is installed behind them, and the incident particles are measured. In the conventional method, the size of the pinholes is about a few mm that is in an entirely different value from actual processing dimensions, and thus it was impossible to accurately measure the incident particles. Further, a differential exhaust system has been required to restrict the changes of energy and charge state caused by the collision among particles in an analyzer tube of an energy analyzer, and the actual measurement on an in-service plasma treatment device was virtually impossible.
As described, a conventional plasma measurement system has a large and complicate apparatus (probe, mass spectrometer, and the like) and causes large disturbance in plasma. For this reason, the most important plasma measurement on a wafer surface where etching reaction progresses in micro nano-scale cannot be performed by the conventional plasma measurement system. In addition, since the cost of apparatus was expensive and so on, it has been difficult to apply it to an actual production apparatus.
Meanwhile, plasma etching of a silicon oxide film is cited as a typical example of the microfabrication processing in the semiconductor manufacturing process. Ions having the energy of a few hundred eV are needed in order to contribute to the etching of the silicon oxide film. In the case of measuring the ion energy distribution by the blocking electric field type energy analyzer, high voltage needs to be applied to a blocking electric field generating electrode.
The object of the present invention is to provide an on-wafer monitoring system capable of monitoring at the position of a substrate, which is an object to be processed, in the plasma treatment device.